However, since the regex must be able to match whitespace-only strings, the entire capturing group is made optional by adding a trailing question mark quantifier.

然而，由于正则表达式必需能够匹配全部由空格组成的字符串，整个捕获组通过尾随一个？量词而成为可选组。

youdao

The trick for capturing amazing group photographs is to break these photography rules. We all have a mind that has infinite creativity.

而拍出令人惊奇的合影的秘密就是要打破这些规矩，我们每个人心中都有无限的创造力，那么好好的利用它呀，一定要敢于打破常规。

youdao

The battle group is the most important in the operation of capturing naval power.

在夺取制海权的作战中，海上战斗兵力群是最重要的。

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At the same time the Indonesian government, which at one point had denied that JI even existed, mounted a sophisticated campaign to dismantle the group, capturing many of its leaders and putting them on trial.

CNN: Should we still fear al Qaeda?

In the past five years, the group has held the population to 50 by capturing, and then adopting out for free, 40 or so newly abandoned horses.

WSJ: Reviving Slaughter of Horses

Colombia's Farc rebel group has said that it intends to carry on capturing military personnel, despite warnings that it could undermine peace talks.

BBC: Colombia's Farc to continue targeting military personnel